The efficacy of immunotherapy by intralesional BCG injection is to be evaluated in patients with primary cutaneous melanoma with poor prognosis (L3 to L5 lesions). The primary variables of interest of this randomized clinical trial - comparing immunotherapy vs. the conventional surgical treatment - are the length of disease-free period, delay of distant metastatic dissemination and length of survival. The procedure to be adopted is: clinical diagnosis, random assignment to immediate wide surgical excision only vs. biopsy, BCG injection followed by same surgery 2 weeks later. Patients under immunotherapy will receive monthly peri-lesional booster of dilute, individually-adjusted BCG for 12 months. L4-5 cases in either group will have regional l.n. dissection 6 - 7 weeks after excision. About 70 patients are expected to enter each arm of this study during 2 years' accrual. Patients will be initially evaluated for general and anti - tumor immune responses by in vivo and in vitro parameters; they will be sequentially monitored for evidence of fluctuations in immunocompetence as well as for correlation of these with treatment and with the course of the disease. The proposed treatment protocol is derived from our own preliminary investigation of the clinical, histopathological and immunological aspects of intra - and peri -lesional BCG in the treatment of primary melanoma.